This invention relates to a conditioned air distribution system of the kind having an air flow duct and a valve in the duct for regulating the volume flow of air through the duct.
This invention relates particularly to an air distribution system of this kind in which the valve is positioned by a pneumatically powered motor.
Systems of this kind are often constant velocity systems but are usually subject to variation in the velocity flow depending upon changes in the room air temperature. The constant velocity regulation has been obtained by sensing the difference between static pressure and total pressure in the duct. However, regulation of the velocity flow in the prior art has been by means of relay mechanisms which introduce unwanted complexity and expense.
It is an important object in the present invention to achieve regulation of the velocity flow by an integrated sensor-actuator. The actuator has a diaphragm which both senses velocity flow and positions a valve in the duct by a direct mechanical connection using the pressures in the duct without a relay.
In many installations the conditioned air distribution system must be able to supply both hot air for heating and cold air for cooling.
Dual duct systems for hot and cold air have been controlled in a way to blend or to mix the hot air flow with the cold air flow to produce the desired amount of cooling or the desired amount of heating. This blending is inefficient because the hot air and the cold air are necessarily fighting against each other. There is a waste of the energy used to produce the hot air and the cold air.
It is an important object of the present invention to control the air flow from a dual duct system in a way such that conditioned air is supplied from only one of the hot and cold ducts at a time without mixing with air from the other duct, except for a possible small overlap required to maintain ventilation requirements.